Method of blowing down and blowing out blast-fuenaces



J. W. DOU

METHOD OF BLOWING N AND B APPL 0N FILED GHERTY.

LOWING our BLAST FURNACES.

MAR. l4, I919.

v 6 m mr 0 3 M ii @8 m m u m m w w M A P p J OHN W. DOUG-HEIRTY, OF BEAVER, PENNSYLVANIA.

METHOD OF BLOWING DOWN AND BLOWING OUT BLAST-FURNACES.

Specification of Letters Patent.

Patented July 8, 1919.

Application flled March 14, 1919. Serial no. 282,683.

To all whom it may concern:

Be it known that I, JOHN lV. DoUoHnn'rY, a citizen of the United States of America, and a resident of Beaver, in the county of Beaver and State of Pennsylvania, have invented certain new and useful Imp-rovements in Methods of Blowing Down and Blowing Out Blast-Furnaces; and I. do hereby declare the following to be a f ll, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to letters or figures of reference marked thereon, which form a part of this specification.

My invention relates to the method of blowing down and blowing out blastfurnaces, and has for its object to increase the safety of these 'operations and to enable the furnace to be blown down to a much lower level than has heretofore been done, without danger of explosions.

In blowing out a blast furnace, as the stock descends the interior volume above the stock line continually increases, and if the furnace is a large one may contain an enormous amount of gas, which, mixed with air, results in disastrous and fatal explosions. Even after the blast has been turned ofi', the furnace is sometimes allowed to stand for a day or more, to be sure that all danger of explosion has passed.

In order to obviate explosions some furnace managers keep the furnace filled with coke during the blowing down operation, so as to maintain the interior of the furnace filled, and when the blast is finally thrown off the coke is quenched with water until cool enough to handle. This coke is then dragged out through an opening made in the bottom part of the furnace. On account of its variable and uncertain content of carbon and of ash it is practically useless, becauseit is a very difficult matter, when using such coke in another furnace, or in the same furnace after it has been relined, to determine just how large a burden the coke will carry.

When the blast is thrown off and the coke is quenched, there is no large space in the furnace filled with gas, and there is no large volume of gas coming through the bell opening. In a short time after the coke is quenched it loses its incandescence. and consequently its ability to form gas, so that the gas mixture remaining in the furnace is nonexplosive. This, however, is an expensive proceeding, as the quantity of coke required 1s very great.

I am aware that it has also been the prac two when blowing down a blast furnace, to

cool the top with water, so that the heat within the furnace will not injure the cast iron or steel parts at the top, and some of thls water is supplied to the furnace through the feeling holes and produces steam, but this steam is insufficient to evacuate the furnace chamber of explosive gas, and the danger of explosion is not avoided thereby.

I am also aware that explosions have been prevented in gas mains by the use of a plug of steam ahead of the gases coming from a furnace, but in carrying out my improved method I introduce within the furnace itself steam in quantities sutlicient to prevent explosion during the blowing out'operations. I therefore have a body of steam or a nonexplosive mixture of gas and steam behind the flow of .gas from about the point at which the gas is generated in the furnace itself and thus drive the gases in front of the steam compelling them to leave the furnace in their usual course, instead of forming a plug of steam in front of the gas column to separate it from the air contained in the gas mains during a blowing in operation.

Referring to the accompanying drawings Figure 1 is a sectional view of so much of a blast furnace as will be necessary for an understanding of my invention.

Fig. 2 is a detail view, partly in section, on a larger scale, of cooling plates for carrying out my invention.

My method is adaptable to blowing down operations, that is to say, where a furnace is blown down to about the mantle, either to examine the interior lining. or inner wall, or to remove a scaffold formed in the furnace. But it is immaterial whether the furnace is blown down for this purpose or is to be blown out for repairs, so far as the ap licability of my invention is concerned.

fter the furnace is blown down and the blast is turned off, it is my object to introduce'into the furnace a material which will fill or occupy the space above the abnormally low stock line, so as to prevent explosion, or the formation of an explosive mixture in the chamber above the stock, and this I do by introducing from above the-normal stock line, indicated approximately atS, steam or other inert gas sufficient to form a non-explosive mixture and then displace the furnace gases.

This may easily be done by introducing a pipe 1 through an opening 2 inthe top of the furnace if it be not too large, through v which water suflicient to keep the pipe from burning out can be supplied as the stock line S descends to the required'level. The

pipe may be introduced through a special When the blast is finally taken off, (either at about the level S or S, accordin to the personal equation and experience 0 the blast furnace manager, or at any other low level,) steam is admitted at a point above the level ofthe stock through the same pipe, thus producing an outward pressure, at once preventingthe entrance of air and its mixture with the hot gasesinside the-furnace and finally from the furnace I t For a 90 or 100. foot furnace such an. ar

rangement would-be difiicult to handle, and

the steam should preferably be'introduced through the side of the furnace at any desired point from the twyers to the top of the furnace.

Under some circumstances it may: be of advantage to cut a hole through the fur nace wall, either above the. mantle or throughthe bosh wall below the mantle,

and introduce a steam pipe,- as shown at 3 and 4, such pipe being fromtwo to three inches in diameter according to the size of the furnace and the quantity of steam necessary to rapidly fill the furnace chamber and maintain it filled after the blast has been taken ofii; This steam mixed with the I gases generated, passes out through the furnace manager.

bleeder B or the bell opening.

- Whether the furnace is blown down to a point above the mantle, as about S, or to a point below the mantle, as about at S,- orto' a point justabove the twyer positions 5, as indicated at S, "or to any other low level, will depend entirely upon the experience and the caution exercised by the I prefer, however, in carrying out the invention, 'to introduce steam and water through the wall of the furnace, either above the mantle or below the mantle, or both,

evacuating all, the gases aeeenee by a permanently installed or temporarily introduced water-cooled plate, or a plurality of such plates, shown for example in Fig. 2, where 6 represents a water-cooled plate built in the; furnace wall above the mantle, exteriorly tapered from its smaller end at or near the inner Wall of the furnace, to its larger end at the outer wall of the furnace. This plate is hollow and provided with pipes 7 and 8 for circulatingthe cooling water for the plate. The exterior taper permits'the plate to be easily withdrawn for repairs, or for the insertion of a new plate, should leaks develop.

Through this plate is a tapered nozzle or opening 9- whose larger endis near the inner wall of the furnace and whose smaller end is i at the outer wall of the furnace Where a short inlet pipe 10 having a flange 11 and a removable plate 12 is connected. Attached to the inlet pipe 10 is a water supply pipe 13 provided with a cut-off valve, as 14,; and a steam supply pipe 15 provided with a cut-off valve 16. The valves may be of any commercial type. a

' The end of the cooler adjacent the inner Wall of the furnace is provided with a more rapidly tapering portion 17, and when the furnace is in operation allor a portion of the nozzle 9 and the tapered portion 17 is filled with brickbats or clay, or both.

When the furnace is to be blown down or out the plate 121s removed, and a tool,

'brickbats removed or bored through and a short plug of wet clay is introduced into the nozzle 9. The plate 12 =is-then replaced, and, preferablyafter the'blast is turned off steam of 150 to 200 pounds is turned on to blow the clay plug in thetube or nozzle 9 and anyinaterl'al left in front of it into the furnace, i v

After thegas has all been driven from the furnace the steam valve 16 is turned off and the water valve 14 is opened to admit'water to euienchfthe s'tockremaining in the .furnace'. a The furnace mancan now proceed to pull out his coolers and twyers and clean out the remainder of the stock in the furnace, taking out the salamander and digging out his inner wall preparatory to putting in a new lining. 3 v

The cooler plate 17 is shown at a point above the mantle; such: a'cooler plate has both steam andwater pipes, as 13 and 15. A plate as indicatedby 18, which is supplied with steam only, may be placed in the bosh of the vfurnace at any desired level, in which case such a plate takes the place of the usual cooling plates for the bosh. This plate may temporarily replace a bosh or inwall plate which has been built in the furnace walls. ()ne or more such plates may be arranged around the furnace. The shape, size and configuration of such a plate will bedependent naturally, upon the volume of steam required to be delivered through it. v V

I have shown the plate 18 as being supplied with steam only, as itis low down in the furnace and not very much above the twyers; it has pipes 19\and 20 for circulatingcooling water, and an'inlet 21 is provided with a flange 22 and-a cover plate 23, similar to like parts described with reference to cooler 6, and a valve 24 for admitting steam.

By my method of blowing out a blast furnace it can be blown down to. or almost to the twyers, so that very little stock remains and little manual labor will be required to handle it.

In addition to eliminating the great danger of explosions, I also save the owner of the blast furnace a great deal of money for labor for removing the'large quantity of stock usually left in a furnace, and the loss of a great deal of time before any attempt Whatever can be made at repairs for placing the furnace in run again.

I claim-- 1. The method of blowing down and blowing out blast furnaces, comprising forming and maintaining within the furnace a non-explosive gaseous mixture at about when the blast is turned off.

2. The method of blowing down and blowing out blast furnaces, which comprises maintalning within the furnace a non-explosive mixture of gas and steam at about when and after the blast is turned off.

3. The method of blowing down and blowing out blast furnaces, which comprises introducing steam into the furnace in quantity sufiicient to maintain a non-explosive atmosphere containing steam therein, and then introducing water into the furnace,

,4. The method of blowing down and blowing out blast furnaces, wluch comprises introducing through the side of the furnace into its interior steam suflicient to maintain a non-explosive atmosphere above the abnormally 10w stock line.

5. The method of blowing down or blowing out blast furnaces, which comprises introducing steam throughthe boshes of the furnace into the interior in quantity sutlicient to produce a non-explosive gas mixture within the furnace.

6. The method of blowing down and blowing out blast furnaces, which comprises maintaining an opening through the wall of the furnace sealed during the normal operation of the furnace, and removing the seal and introducing steam through said openin at about the time the blast is turned off.

The method of blowing down and blowing out blast, furnaces, which comprises maintaining an opening through the wall of the furnace sealed durin the normal operation of the furnace, and removing the seal and introducing steam and thereafter introducing water through said opening at about the time the blast is turned off.

8. The method of preventing explosions in blast furnaces when blowing down or blowing out, which comprises introducing steam into the furnace at about the point of gas generation after the blast has been turned off.

In testimony that I claim the foregoing as my invention, I have signed my name hereto.

- JOHN W. DOUGHERTY. 

